Bottom pre-breaking mechanism for a carton forming machine

Claim 1

In a carton forming machine for forming selectively either small or large paper cartons from blanks having sidewalls adapted to be opened to form a body portion of a rectangular cross section and bottom panels integral with the sidewalls and adapted to be folded and sealed to close the bottom of the carton, said machine having a bottom panel prebreaking station and means for advancing an opened carton to and for supporting the same at the prebreaking station, and prebreaking mechanism comprising: a pair of fingers of substantially identical shape; means for mounting said fingers in opposed relation substantially normal to and aligned with the longitudinal center line of an oPposed pair of the side walls of a carton at the prebreaking station and for movement endwise of the axis of the carton between an operative and an inoperative position and for pivotal movement in the operative position between a prebreaking position and a pivotally retracted position; means for imparting said endwise and said pivotal movement to said fingers; said fingers having opposed first edge portions that are substantially straight and parallel to the carton axis in the pivotally retracted position of the fingers and are spaced apart a distance greater than the transverse dimension of the small cartons and less than the transverse dimension of the large cartons, said first edge portions having leading end portions, and second edge portions inclined outwardly at an acute angle relative to the carton axis from the leading ends of the first edge portions and having tips disposed outwardly of the sidewalls of a large carton to permit said second edge portions to engage free edges of a respective opposed pair of said bottom panels upon endwise movement of the fingers from the inoperative to the operative positions to cam the same inwardly, said tips being disposed relative to the pivot axes of said fingers for movement from positions outwardly of the sidewalls of a large carton to positions adjacent to the carton axis upon pivotal movement of said fingers, the path of movement of said tips being essentially normal to the carton axis and intersecting the bottom panels adjacent the upper portions thereof; and a pair of levers for engaging and inwardly bending an opposed pair of bottom panels intermediate the pair engaged by said fingers, said levers being pivoted on said finger mounting means and having cam means cooperating with cam follower means on said means for imparting movement to the fingers to impart pivotal movement to said levers.